Apparatus for manufacturing screens



June 26, 1951 Filed July 26, 1948 J. A. GIB BONS APPARATUS FOR MANUFACTURING SCREENS 3 Sheets-Sheet l 16 16 L W I 4 INVENTOR. JflMES A7. G/BBONS "WM/W June 26, 1951 J. A. GIBBONS 2,558,244

' APPARATUS FOR MANUFACTURING SCREENS Filed July ,26, 1948 v 3 Sheets-Sheet 3 5'2 I SCREEN w/TH 05 E MQTE/X' $g.8; INVENTOR.

JHMES' ,Q. G/BBONS HTTOQNEV Patented June 26, 1951 APPARATUS FOR MANUFACTURING SCREENS James A. Gibbons, North Hollywood, Calif., as

signor to Warner Brothers Pictures, Inc., Burbank, Calif., a corporation of Delaware Application'july 26, 1948, Serial No. 40,667

This invention relates to. an apparatus for the manufacture of screens, such as light reducing screens or similar types of plastic screens for use in the .productionor. showing of. motion pictures.

In my copending. application, .Ser. No. 40,666, filed July 26, .1948, a methodof. making and using a neutral density light reducing screen has been disclosed and claimed, such a screen being produced on. apparatusand on a. matrix. made by the method and system described hereinafter. The matrix consists of a plurality of layers, some of which are applied inmore than one coat; each layer having a specific function. The apparatus for forming or casting the matrix layers includes a cylindrical drum especially constructed and which may be varied in rotation to vary the application of each layer. It has also been found that by arranging strings between certain layers of the matrix, different layers may be removed'in the event of damage to only certain of the layers. Therefore, an entirely new matrix need not be cast. The present-apparatus is flexible to produce both the matrix and screens having the desired light diffusing or transmitting qualities.

The principal object of the invention, there'- fore, is to facilitate the manufacture of light diffusing or transmitting screens.

Another object of the invention is to'provide an improved apparatus for manufacturing light transmitting or difiusing screens.

A further object of the invention'is'to provide an improved system for controlling the application of solutions to a large surface to provide both a matrix and the light screens formed-thereon.

A still further object of the invention is to provide an improved means for forming and removing a screen after the formation thereof.

Although the novel features which are believed to be characteristic of this invention will be pointed out with particularity in the appended claims, the manner of its organization and the mode of its operation will be better understood by referring to the following descriptiomread in conjunction with the accompanying drawings, forming a part hereof, in which:

Fig. 1 is an end view of the drum and solution tank embodied in and for performing the invention.

Fig. 2 is a front, elevational view of the tank and dip-pan of Fig. 1.

Fig. 3 is an end view of the drum and dip-pan in a different relationship to that shown in Fig. 1-. Fig. 4 is a partial front View of a drum showing the arrangements of the cutting cords for the reinoval of different layers of the matrix.

13 Claims. (01. 1815) Fig. 5 is a cross-sectional view of a section of the drum showing the method of application of the various coats and layers of the matrix.

Fig. 6 is a detailedcross-sectional view, similar to Fig. 5, showing the final application of the screen upon thematrix, and w h Figs. 7 and 8 are detailed views of the screen after application of the screen and dye.

Referring now to the drawings, in which the same numerals identify like elements, a cylindrical drum 5 is constructed of suitable materials such as wood land of the size desired for the manufacture ofthe largest screen. The'drum being describedwasapproximately five feet, ten inches, in diameter. The facing material is of kiln-dried fine grain wood of medium hardness to give a smooth constant convex surface from the axis of the drum. It is water-proof glued and coated on its inner surface to resist moisture absorption. The drum has axles 8 mounted on solid non-vibrating pylons 6 in bearings I. The drum is hollow and has a longitudinal slot 9 cut therein, as shown in Figs. 1, 3, and-4. The slot is sufficient in width so that its edges may clear the liquid to be'applied in rotation. The present slot was approximately fifteen inches in width. The drum is connected through a chain or belt to a driving motor (not shown) which may have its speed controlled so that any desired speed of rotation of the drum Smaybe obtained.

Mounted on a truck I2, which is movable on a track [3, is a stainless steel dip-pan I 5, the pan being mounted on a pair of hydraulic screw jack elevators l6-so that the pan may be raised or lowered for removing the'liquid from the drum, and for cleaning the pan l5, or for changing liquids. The pan has a concave curvature of approximately the same radius as the drum 5, the closed ends of the pan extending at least one inch beyond the ends of the drum. As shown in Figs. 1 and 3, a liquid solution I! of the various types explained hereinafter is placed in th pan [5. Optimumlevelof the solution I? is such that the width of the surface of the solution is approximately seventeen inches.

The face of the'drum is trued for curvature'by rotation of the drum during lateral movement of a cutting and sanding tool mounted on a nondeviating track parallel to the axis of the drum; After the face of the drum is completed, it is treated with a layer 200i furiural plastic Furane X2 with an acid catalyst added, and kept at an approximate temperature of one hundred degrees F. to accelerate the curing of the resin. This is the first layer of the matrix and approximately six coats are applied, each coat being cured before the next coat is applied. Adjustment is made to allow for thickness of these furfural plastic coats, and the face of the drum re-trued with coarse-cut to fine-cut as finish is approached by rotation of the drum and lateral movement of the sanding tool as set up previously. The drum is mounted in a suitable dust-proof room or housing, in which there is a door for accommodating the pan and inspection windows. The room or housing is then supplied with dust-free air at an approximate humidity of 50/50, the air being heated to approximately eighty-five degrees F. to assist in relieving the solvents from the deposited resins.

Three coats of a layer 2| of the following formula are then applied directly on the trued furfural plastic surface, the formula being referred to as M-3, for the purpose of explanation:

Ethyl cellulose gms 744 Xylol cc 3468 Ethylene glycol monomethyl ether cc 827 Butyl alcohol cc 827 Methyl isobutyl ketone cc 827 Methyl phthalyl ethyl glycollate cc 48 Each coat of M-3 is applied at a drum speed of one revolution in sixteen minutes, each coat being dried under blower and heat. This layer is for the purpose of preventing the water of the next layer from entering the pores of the furfural plastic and getting into the wood of the drum 5. Since the furfural plastic and M3 layers reach only to the point 23 by the rolling process (see Figs. 5 and 6), the solution is brushed on from point 23 to point 24 to protect the drum and to insure that the matrix extends beyond the screen edges. The other coats of the matrix now to be described are also similarly brushed on between points 23 and 24, the screen layers cast on the matrix extending only to point 23.

The next layer 26 of the matrix is a low vis cosity water soluble polyvinyl alcohol known as Evanol 683-05, and hereinafter referred to as PVA. This solution is made by slowly adding 1500 grams of polyvinyl alcohol to 5450 cc. of distilled Water at between seventy and eighty degrees C. then, mixing one hundred cc. of distilled water with six gms. of a surface tension reducing agent such as sodium sulfonate of an alkyl oleate and three hundred gms. of tricresyl phosphate. The two solutions are then mixed, and sufiicient water is added to make 1000 cc., the final solution being filtered and allowed to stand twelve hours before placing in pan l5. One hour setting time in the pan is allowed for checking for bubbles and removing any that exist. This layer forms a protection to the finish of the drum by withholding active solvents from the furane.

This polyvinyl alcohol layer 26 is a single coat and is applied in one revolution of the drum in fourteen minutes, then dropping the pan and revolving the drum at the rate of eight minutes per revolution until the coat is dried, air and heat being applied. The approximate drying time is four hours. To prevent flow back as the viscosity changes by application, the fourteen minute speed is maintained for approximately /4 revolution of the drum before it is increased to the eight minute speed. The edges between points 23 and 24 are brushed on as for the first layers.

The next layer 21 is two coats of a copolymer of vinyl chloride and vinyl acetate solution made up as follows:

Vinyl acetate vinyl chloride 0 o p o ly- The viscosity of this solution is adjusted to thirty-seven at twenty-four degrees C., the plasticizer, methyl phthalyl ethyl glycollate, being put into solution at seventy degrees C. The solution is applied at one revolution in sixteen minutes.

The M--3 coats applied to the furfural plastic face are not solvent reactive, and, as mentioned above, prevent pitting reaction against the PVA layer that protects the drum face from solvent damage of later layers. The copolymer of vinyl chloride and vinyl acetate layer prevents a reaction of the contained water in the polyvinyl coating, and the acetone of the next layer 28, which will be called, for purposes of description, 8.3, and which is as follows:

Hercules cellulose acetate gms 400 Acetone cc 1995 Ethanol cc 215 2 Nitro propane cc (715) Ethylene glycol monomethyl ether acetate cc (715) Toluene cc (383) Methyl phthalyl ethyl glycollate cc 200 The three bracketed diluents are used to adjust Viscosity to thirty-seven at twenty-four degrees C. This layer is applied in three coats, each coat at a speed of one revolution of the drum in twelve minutes, the edges being well brushed for binding the acetate to the drum. The 8.3 layer 28 is plasticized to check shrinkage tension from reaching the breaking point.

The last layer 29 of the matrix is called 8.3M, it being the same as the 8.3 layer 28, except that it is unplasticized. Two coats of 8.3M are applied at a drum speed of one revolution per coat in twelve minutes, the drying time being twelve hours. The purpose of this layer is to provide an exceptionally high gloss and smooth surface to the matrix necessary for filter clarity. The plasticized layer 8.3 would give a slight diffusion (star gaze) which is detrimental to the clarity of images in the final filter screen made thereon. All viscosities are based on Stromer viscometer readings, one minute time, one hundred gm. Weight.

Referring to Figs. 4 and 5, a plurality of five strings or cords 32 to 36, inclusive, are shown interposed between the various layers just described. The cord 32 is on top of layer 20 and under layer 2|, each cord being laid and the ends fastened by tacks or other suitable means at 38. A similar set of cords 31 is employed at the other end of the drum. Horizontal cords, such as shown at 39, are inserted between the layers and tacked at their ends as shown at 42 in Fig. 3. It will be noted that no horizontal cords are along the other side of slot 9, but are on the trailing edge of the surface. This cord arrangement prevents the cords picking up an excess of solution and causing flow back which forms streaks.

The purpose of the cords is to permit any number of layers of the matrix to be stripped from the drum without going down to the furane layer whenever certain layers of the matrix have been damaged. For instance, if the damage only extends through the outside two layers, then by pulling strings 35, the upper two layers will be are;

cut and may be easily removed'froin the matrix, new layers then being applied. Each" layer is thus accessible, and the "entir'ema'tii'x need not be removed when onlyone'o'r more of the outside layers need replacing. In most instances, -cutting cords 36 between the 8.3 and 8.3M layers is sufficient, as the damage does not usually extend beyond the 83M layer.

The matrix is now ready for the manufacture of neutral or dyed screens such as descril'oe'd in my above mentioned cop'end'ing application. For instance, the base of a dyed screen may be made from the above M3 formula, siX coats 45 to 50, inclusive, (see Figs. '6, '7, and '8) providing a screen approximately .007 inch thick. The viscosity of the solution and speed of rotation of the drum are adjusted to give 'free flow and great leveling power. Although thefscreen has been shown in Figs. 6, '7 and 8' in layers, for illustration, it actually becomes homogeneous upon drying, no lines of demarkation between coats being Visible. I I I The final coat should be dried two hours before applying the following dye and solvent formula which provides a neutral density of substantiall-y sixty-five percent absorption and one providing a balance between the light intensity of a bright sun and normal interior illumination:

Solvents- The dye solvents and filter dye solution are absorbed by the M3 layer to various extents, depending upon the spee'd'df the matrix or drum. For instance, over each three 'ieet'of a matrix surface, the speed may be varied to provide test strips from which a graph of light transmission or absorption versus drum speed may be made. The correct drum speed for a certain value of "absorption is thus found 'forproducing the final screens. correct to bring the desired absorption value within the limits "of drum speeds necessary for uniform application of the dye coat, the dye solu- "tion may be strengthened or weakened in the same proportions as given above.

As explained in connection with the matrix, a cord 52 is shown just under the outside layer '50, this cord being at one end of the drum, another similar cord being at the other end of the drum, and one cord being strung lengthwise of the drums as shown at 39. The solvents cause the cord to shrink, and it becomes integral with all layers of the screen so that by removing the cord 52, the screen is cut to the 8.3M layer of the matrix, and thus, easily stripped therefrom without damage to the matrix. The showing of the cord 52 and screen layers are enlarged and exaggerated to illustrate the embedding action of the cord.

In addition to the manufacture of the light If the above dye -proportions are not 6 balancing or absorbing screen 'justdescribed, rear-projection light difiusing screens for process photography or picture exhibition may also be formed with the apparatus of the invention. In -making such screens, the same matrix is used as for the filter screens, except that the 83M, or last layer of the matrix on which the screen is formed, is changed to a layer containing a grit for introducing light diffusion, This layer is similar to the 8.3 to 8.3M layers and has the following formula:

Hercules cellulose acetate gms 659 Aceton cc 1112 Ethanol cc 215 2 Nitro propane cc 2000 ,Meth'yl Cellosolve acetate cc 1334 Toluene cc 890 Methyl .ph'th'alylethyl glycollate p'lasticizer) -sl l a cc 329 600 Carborundum-grit gms. 908

The cellulose acetate is first dissolved in the acetone and ethanol to which the plasticize'r and grit are added. 'The mixture of nitro propane, methyl Cellosolve and toluene then dilutes the formula to a viscosity of ninety-three at twentytwo degrees C. This layer is applied to the 8.3 layer in one or two coats, each coat b'eingapplied in one revolution of the drum-in fourteen minutes, which evenly and uniformly distributes the grit over the matrix.

To form a rear-projection screen, the same method of forming the base of the filter screen is followed, th grit in the last matrix layer pro viding a light diffusing surf-ace which is efficient and uniform over its entire surface. Cutting strings for the-removal of the screenmay beused in the same manner as described above for removing the filter screens from the matrix.

I claim:

'1. A device for manufacturing screens from solutions of different viscosities, comprising a drum adapted to be rotated atdifferent-speeds in accordance with the viscosity of thesolution and the thickness of the layer to be formed thereby, said drum being cylindrical with wood facing,

the inner surface thereof being water-proof glued, said drum having a longitudinal opening therein, a horizontal pan having a width. comparable to the width of said opening and extending the length of said drum and adapted to be moved under said drum, means for raising and lowering said pan equally at all points thereon, and means for transporting said pan to and from under said drum, said means including a truck on which said pan and said pan raising and lowering means is supported.

2. A screen matrix comprising a layer of furfural plastic, a water checking layer, a layer of polyvinyl alcohoL-a layer of a copolymer of vinyl chloride and vinyl acetate, a layer of plasticize'd ce'llulose acetate, and a final layer of unplasticized cellulose acetate.

3. A screen matrix in accordance with claim 2, in which said water checking layer is formed from a solution substantially as follows:

Ethyl cellulose gmS 744 Xylol cc 3468 Ethylene glycol monomethyl ether cc 827 Butyl alcohol cc 827 Methyl isobutyl ketone cc 827 Methyl phthalyl ethyl glycollate cc 48 4. A screen matrix in accordance with claim 2, in which said polyvinyl alcohol layer is formed from a mixture of solutions A and B whose compositions are substantially as follows:

A. Water (Distilled) cc 5450 Polyvinyl alcohol gms 1500 B. Water (Distilled) cc 100 Sodium sulfonate of an alkyl oleate gms 6 Water to make cc 1000 Tricresyl phosphate gms. 300

5. A screen matrix in accordance with claim 2, in which said copolymer of vinyl chloride and vinyl acetate layer is formed from a solution substantially as follows:

Vinyl acetate vinyl chloride copolymer gms 500 Butyl acetate cc 2625 Methyl phthylate ethyl glycollate cc 37.5

6. A screen matrix in accordance with claim 2, in which said plasticized cellulose acetate layer is formed from a solution substantially as follows:

Cellulose acetate gms 400 Acetone cc 1995 Ethanol cc 215 2 Nitro propane cc 715 Ethylene glycol monomethyl ether acetate cc 715 Toluene cc 383 Methyl phthylate ethyl glycollatecc- 200 '7. A screen matrix in accordance with claim 2, in which said unplasticized cellulose acetate layer is formed from a solution substantially as folfural plastic, a water checking layer, a layer of polyvinyl alcohol, a layer of a copolymer of vinyl chloride and vinyl acetate, and a layer of plasticized acetate.

9. A screen matrix in accordance with claim 8, in which said final layer is substantially as follows:

Cellulose acetate gms- 659 Acetone cc 1112 Ethanol cc 215 2 Nitro propane ccu 2000 Methyl Cellosolve acetate cc 1334 Toluene cc 890 'Methyl phthylate-ethyl glycollate (plasticizer) cc 329 10. Apparatus for forming screens from solutions of different viscosities, comprising a cylindrical hollow wooden drum water-proof glued and adapted to rotate on a horizontal axis, said drum having a longitudinal opening therein of substantially one-fifteenth of the circumference of said drum, an elongated pan having a bottom surface of substantially the same curvature as said drum and a width comparable to the width of said opening, truck means for transporting said pan to and from under said drum, the horizontal axis of said pan being parallel with the axis of rotation of said drum, and means carried by said transportation means for raising and lowering said pan equally at all points thereon.

11. A screen matrix in accordance with claim 2, in which cords are positioned adjacent certain edges of and between said respective layers to permit the removal of any selected number of layers simultaneously.

12. A device for manufacturing screens from solutions of different viscosities, comprising a wooden surfaced drum adapted to be rotated at different speeds in accordance with the viscosity of the solution and the thickness of the layer to be formed therefrom, said drum being cylindrical with a longitudinal opening in the surface thereof, a horizontal pan extending the length of said drum and adapted to be moved under said drum, means for raising and lowering said pan, and a solution in said pan contacted by said cylindrical surface of said drum when rotated, said solution being varied for forming different layers on the surface of said drum as said drum is rotated at appropriate speeds, said wooden surface being covered with a matrix of a layer of furfural plastic, a Water checking layer, a layer of polyvinyl alcohol, a layer of a copolymer of vinyl chloride and vinyl acetate, and a layer of cellulose acetate.

13. A device for manufacturing screens in accordance with claim 12, in which cords are positioned adjacent certain edges of and between said layers to permit the removal of any selected number of layers simultaneously.

JAMES A. GIBBONS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'IENIS Number Name Date Re. 8,407 McNamee Sept. 10, 1878 1,008,607 Mellinger et a1 Nov. 14, 1911 1,981,472 Schneider Nov. 20, 1934 2,140,518 Doolittle Dec. 20, 1938 2,198,621 Izard Apr. 30, 1940 2,223,327 Light et al Nov. 26, 1940 2,345,013 Soday Mar. 28, 1944 OTHER REFERENCES Vinylite Resins, Carbide and Carbon Chemicals Corporation, 1942, page 4. (Copy in Division 15.) 

